The 3rd Generation Partnership Project (3GPP) is a telecommunications standards body formed of a number of organisations with telecommunications interests. The stated aim of 3GPP is to make a globally applicable third generation (ITU) mobile phone system specification within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). 3GPP has issued a set of standards (referred to as releases) each release adding further functionality to the existing releases. Release 98 and previous releases defined “second generation” GSM networks; Release 99 introduced “3G” UMTS networks; Release 4 introduced principally architectural changes including an all IP core network; Release 5 introduced IMS (IP Multimedia Subsystem) and HSDPA (High Speed Downlink Packet Access); Release 6 introduced integrated operation with Wireless LAN networks, HSUPA, (High Speed Packet Uplink Access) and further developments of IMS such as Push to Talk over Cellular (PoC); Release 7 (as yet finalised) will provide a number of further refinements particularly with respect to the WCDMA air interface, and Release 8 (expected in 2009) is being defined to introduce a number of significant changes including RAN Long Term Evolution with new access technologies and new core network architectures to support different access networks for both 3GPP defined access networks as well as non-3GPP access networks.
Due to these continuing enhancements of functions and definition of new access networks and architectures introduced in different releases issued by 3GPP, many current 3GPP compatible networks include multiple radio access technologies for providing voice and data services to mobile devices. Such radio access technologies include circuit GSM, GPRS, EDGE (Enhanced Data Rates for GSM), UMTS/UTRAN RAN LTE and non-3GPP access technologies such as WLAN, Wimax and CDMA/CDMA2000.